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| Author | Topic:Temperature and measured permittivities (5TE) | 558 Views |
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Temperature and measured permittivities (5TE)
26 March 2012 at 4:09am Last edited: 26 March 2012 5:58am
Hello everybody,
I'm a student and currently working with the 5TE probes for my course. I've worked on the bulk density, water volumic content and temperature effects on the measures of permittivity. The experimentations about the effect of temperature have lead me to make a graphic :
The problem is that when the temperature increases, the dielectric permittivity décreases for a WVC of 0.40 m3.m-3, but increseases for lower VWC. Could you give me some infos concerning the phenomenon? Is there a VWC for what the temperature doesn't affect the permittivity?
PS: The bulk density of the sample is 1.6, "Epsilon" is the dielectric permittivity that is measured by the 5TE probes.
PS2 : The leading coefficients of the curves decrease with the increasing of the VWC.PS3 : Sorry for my bad english skills, I stay connected if you have questions
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Re: Temperature and measured permittivities (5TE)
26 March 2012 at 4:00pm Last edited: 27 March 2012 7:25am
The relationship between dielectric permittivity and temperature is kind of tricky for soils. The dielectric permittivity decreases for water as the temperature increases, so at higher water contents this trend would dominate. Every soil will have a unique relationship though, and a different sensitivity to changes in temperature. We usually recommend a multivariate approach post-analysis to correct for temperature (http://www.decagon.com/education/correcting-temperature-sensitivity-of-ech2o-soil-moisture-sensors-13394-02-an/) variation in water content. We do not understand the phenomenon well enough to implement a mechanistic approach (yet).
I hope this helps...
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Re: Temperature and measured permittivities (5TE)
27 March 2012 at 6:07am
Thank you fot this quick answer, now I understand what are the real factors of the dielectric measures.
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